1. Field of the Invention
This invention relates to an inlet guide vane control device of a gas turbine comprising a gas turbine body, a combustor, and a compressor with an inlet guide vane.
2. Description of the Related Art
A gas turbine, which comprises a gas turbine body, a combustor, and a compressor with an inlet guide vane (IGV), is equipped with various control devices and protective devices, such as an IGV control device for exercising opening control of IGV, and a fuel control device for controlling the amount of fuel supply to the combustor.
A conventional IGV control device determined an IGV opening command based on a gas turbine output corrected with the intake air temperature of the compressor (the temperature of the air flowing into the compressor) (corrected gas turbine output: the product of a correction factor, set as a function of the intake air temperature, and gas turbine output), and effected the opening control of IGV according to this command. The reason why the gas turbine output is corrected with the intake air temperature is that the IGV opening command is determined in consideration of the density of air differing according to whether the intake air temperature is high or low.
Patent document 1 indicated below describes an antisurge control device of a gas turbine. Patent document 2 shown below describes gas turbine equipment provided with a control device for performing IGV opening control such that the exhaust gas temperature becomes a predetermined temperature.
Patent document 1: Japanese Patent Application Laid-Open No. 1998-47079
Patent document 2: Japanese Patent Application Laid-Open No. 2003-206749
The above-described conventional IGV control device only determines the IGV opening from the gas turbine output corrected with the intake air temperature, and does not effect the following types of control:    (1) IGV opening control such that the temperature of the exhaust gas discharged from the gas turbine body does not reach the exhaust gas temperature limit.    (2) IGV opening control such that the pressure ratio of the compressor (the ratio between the inlet pressure and the outlet pressure) does not reach the surge limit of the compressor.    (3) IGV opening control such that the pressure of the exhaust gas (combustion gas) discharged from the gas turbine body (i.e., gas turbine back pressure) does not reach the gas turbine back pressure limit value.
If the exhaust gas temperature or the exhaust gas pressure (gas turbine back pressure) become too high, damage to or breakage of an exhaust duct may be induced. If the pressure ratio becomes too high, surging may occur, causing damage to or breakage of the compressor. Thus, with the IGV control device, it is also necessary to exercise IGV opening control in consideration of the exhaust gas temperature, the pressure ratio of the compressor, and the exhaust gas pressure. In the protective device of the gas turbine, when the exhaust gas pressure reaches a predetermined value, for example, the gas turbine is brought to an emergency stop and, when the pressure ratio or the exhaust gas temperature reaches a predetermined value, a certain protective function is performed. In order to ensure the continued operation of the gas turbine (increased rate of operation) while reducing the possibility that the protective function, such as emergency shutdown, is performed, there is need to perform IGV opening control in the IGV control device, with the exhaust gas temperature, the pressure ratio of the compressor, and the exhaust gas pressure being taken into consideration.
The antisurge control of patent document 1 and the exhaust gas temperature control of patent document 2 mentioned above are each performed individually, and do not correspond to IGV opening control taking the exhaust gas temperature, the pressure ratio of the compressor, and the exhaust gas pressure into consideration.
The present invention has been accomplished in light of the above-described circumstances. It is an object of the invention to provide an inlet guide vane (IGV) control device which can exercise IGV opening control taking the exhaust gas temperature, the pressure ratio of the compressor, and the exhaust gas pressure into consideration.